A cyclotron clock display, mounted on a wooden base. There are two stepper motors exposed on either side. There is a panel installed in the wooden base with a red button on the left, two knobs and four smaller buttons in a two by two grid on the right.

A Flipping, Perpetually-Rotating Clock

Clocks are a mainstay of hackers and makers, as they provide a way to explore creative designs while still maintaining a functional aspect to the project. [Brett Oliver] follows this tradition in making a cyclotron clock that uses a perpetual rotating digit concept from a 1900s desk flip calendar.

An exploded view of one of the flip calendar digit display, showing how the tiles fit into the chamber.

Each digit of the clock has a rotating chamber that’s big enough to fit a group of tiles inside that have digits printed on either face. The tiles are sized and stacked in such a way that the rotation of the chamber allows the next tile to slide in front of the old one. Specific digits are revealed by rotating the chamber a number of times.

Each of the four digits positions has a 28BYJ-48 stepper motor to rotate the chamber, with each motor being driven by a ULN2003 driver module. The main microcontroller is a ESP32 WROOM, and an I2C compatible DS3231 real time clock (RTC) module keeps time. All of the motors are driven off of an LM2596 module that provides 7 V, while the ESP32 and RTC are powered from a USB connector.

The different modes and the ability to set time is done through a panel that has various buttons and knobs. The whole clock is mounted on a custom wooden base that has cutouts for the panels and cabling. [Brett Oliver] has done a great job of documentation, going into detail about the mechanics and electronics of the build. Design files, including STLs of the various components, are also available for download. Be sure to check out the video after the break.

We’ve featured a flip calendar with a similar operating principle before which clearly shows the inner workings of the mechanism.

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DIY Perpetual Flip Calendar

Flip calendars are a neat little piece of history. Sold as tourist trinkets, they sit on your desk and show the current day of the month and, depending on the particular calendar, month and year. Each day, you rotate it and it shows you the current date. At the end of February, you rotate it a bunch of times to get from February 28th (or 29th) to March 1st. [measuredworkshop] always had fun flipping the dates on his parents’ flip calendar, so decided to build his own wooden one.

The calendars consist of a series of tiles with the dates on them inside an enclosure. Rotating the enclosure allows a new tile to slide down in front of the old one. Once you know how many tiles you are going to use, you put a different date on the back side of each tile. In [measuredworkshop]’s case, there were 15 tiles to hold 30 dates (he created one with 30/31 on it for the end of the month) so the 1 has a 16 on the back, the 2 a 17, and so on. Tiles of different colored wood were cut and sanded and then the numbers drawn on by hand.

The enclosure was cut using a Morso Guillotine, a machine which uses sharp blades to do precise mitre cuts in wood. One side of the enclosure was covered by wood, the other by clear acrylic, so that you can see how the mechanism works as it is rotated. Finally, a stand was cut from wood as well and the final product assembled.

As you can see in the video below this is a great showpiece, and because of the design gives a view into how flip-calendars work. At the end of his write-up, [measuredworkshop] shares a link he found to a 3d printed flip-calendar on Thingiverse. Check out some of the more techie calendars posted at Hackaday, like this e-ink calendar, or this Raspberry Pi wall calendar.

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